1. Field of the Invention
The present invention relates to a network device in a data network and more particularly to a system and method of creating a logical port by logically linking multiple ports and for transmitting unicast packets through the logical port.
2. Description of the Related Art
A packet switched network may include one or more network devices, such as a Ethernet switching chip, each of which includes several modules that are used to process information that is transmitted through the device. Specifically, the device includes an ingress module, a Memory Management Unit (MMU) and an egress module. The ingress module includes switching functionality for determining to which destination port a packet should be directed. The MMU is used for storing packet information and performing resource checks. The egress module is used for performing packet modification and for transmitting the packet to at least one appropriate destination port. One of the ports on the device may be a CPU port that enables the device to send and receive information to and from external switching/routing control entities or CPUs.
A current network device may support physical ports and logical/trunk ports, wherein each trunk port includes a set of physical external ports and the trunk port acts as a single link layer port. Ingress and destination ports on the device may be physical external ports or trunk ports. By logically combining multiple physical ports into a trunk port, the network may provide greater bandwidth for connecting multiple devices. If one port in the trunk fails, information may still be sent between connected devices through other active ports of the trunk. Therefore, trunk ports enable the network to provide greater redundancy between connected network devices.
In order to transmit information from one network device to another, the sending device has to determine if the packet is being transmitted to a trunk destination port. If a destination port is a trunk port, the sending network device must dynamically select a physical external port in the trunk on which to transmit the packet. The dynamic selection must account for load sharing between ports in a trunk so that outgoing packets are adequately distributed across the trunk.
Typically, each packet entering a network device may be one of a unicast packet, a broadcast packet, a muliticast packet, or an unknown unicast packet. The unicast packet is transmitted to a specific destination address that can be determined by the receiving network device. However, the sending network device must select one port from the trunk group and adequately distribute packets across ports of the trunk group.